Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
H, W = map(int,input().split())
s = []
black = 0
for i in range(H):
    tmp = list(input())
    s.append(tmp)
    for j in range(W):
        if tmp[j] == "#":
            black += 1
white = H*W - black
 
 
q = [(0,0,0)]
s[0][0] = "#"
while q:
    i, j, cnt = q.pop(0)
    for di, dj in [(1,0),(0,1),(-1,0),(0,-1)]:
        ni, nj = i+di, j+dj
        if ni == H-1 and nj == W-1:
            print(white-cnt-2)
            exit(0)
        elif 0 <= ni < H and 0 <= nj < W and s[ni][nj] == ".":
            s[ni][nj] = "#"
            q.append((ni,nj,cnt+1))
print(-1)